Article made from plastic material and method of making the same



Jan. T. GRIFFITHS ARTICLE MADE ERoM PLASTIC MATERIAL AMD METHOD @E MAKING THE SAME Filed May 2. 1924 2 sheets-snee@ I Jan. 1l 1927. 1,613,993

R. T. GRIFFITHs ARTICLE MADE FROM PLASTIC MATERIAL AND METHOD OF MAKING THE SAIIE Filed May z 1924 2 sheets-sheet 2 gwvemkoz E E 5Min,

Patented Jan. 1l, 1927.

UNITED' STATES PATENT OFFICE.

RICHARD T. GRIFFITHS,i OFfAK'RON, OHIO, ASSIGNORITO THE'MILLER RUBBER COM- PANY, OF -AKRON, OHIO, 'A CORPORATION OFOHIO.

ARTICLE MADE FROIVL PLASTICMATEBIAL AND yME'IIIOD OF MAKING THE SAME.

Application filed May 2,.,1924.

My present invention relatesl to the manu- 'lacture oi tubular rubber articlesand more pa rtieularly to the manufacture of resonatin g horns tor use in connefl'ion with loud speal i ing devices, phonographs. or similaisound producing instrunients, and the invention in cludes the novel,artifleanfl method ot making the same herein described, and deiined by the appended claims.

lt has been 'found that sound conducting bodies such as horns used on loud speaking devices and iviihonographs are best wheni'nade oll such a material that 'the horn itself does not set up Yilnationsot its own whereby dis- 15 coi-dant or distortantsounds wouldbeadded to the speech or music which it is the purpose olf the conductingl body to convey trom the Vibrating diaphragm to the air in the room.

Experiments have shown that when such 20 sound conduits are made ot cellular hard rubber, they are particularly tree from seltribration, or the material is of such a nature as to elliectually damp such Vibrations as might ordinarily originate therein.

This material prepared in plastic torni which when placed in a mold having the shape ol the bornand subject ed to heat will @pand deze to the blowing substance containefl therein, Auntil the plastic completely le* lills the molds aud. as a yulcanizable plastic is used, vulcanization olE this plastic takes place during the expanding process, so 'that a ri liar-ticle completely filling the mold is 'form-ed thereby.

JF 'lhese horns are oi such peculiar and sinuous shape that great. dilliculty has been 3. `erienced in prm'iding suitable cores wl c ccnl-:l be removedirom the article after it had be; ome hardened or vulcanized, such cores being necessary to properly shape and hold the interior surface of the plastic duringl rulcanizati-on, and in many i'orms ot horns the shape has been such that it has been :lound that the shape so coim'ilicates 'i5 the core as Jto-number of parts that it' has serial No. 71o.659.

Fig. Q is an elevation.

Fig. 3 isa section on line 3 3 oi Fig. 2, and

Fig. l is an elevation ot the horn partly broken away.

Figs. 5 to 9 are detail viewssomewhat enlarged or exaggerated for clearness ot illustration.

`In .the drawings above referred to, I have shown a m-old such as has been customarily used'in producing horns of the character described, which tomprises a pair ofrom* pleinentary longitudinally divided sections l and ln detachably held together by bolts L. 3 designates a core section tor torni-ing the larger flaring end ot the horn, troni which. due to its large and flaring shape, it is easily ren'ioyable, this core sect-ion haying a marginal tiange El, which is detachably secured to the corresponding margin ot'. mold sections l and l by bolts, or like fastening means indicated at ei.

The portion oi? the interior of the mold not occupied by the core section 3 must be provided with a core in order to shape and sustain Vthe plastic material and it has hereto't'oreV been the practice to supplement said core 3 with additional core sections detacln ably connected to each other and to lthe seetion 3, and this has been i'oiid to be a dii'ricult problem, and thus tar no practicable solution ot the problem has been found.

In order to ayoid the above diilieulty and malte possible manufact-nre oif horns oiE sinn-oas shape, I provide a metal reinforcement (l, .which may be made trom sheet z,

metal in. one or more parts, the one I hare illustrated being shown as consisting of two parts, G and 6, which may be welded together alter torming, as shown in Fig. 9 at 6, or fastened by any other well known means so as to produce an approximately conical article having the desired sinuosity, and substantially smooth surfaces` as tor example by loch seam, as shown at G in Fig. 8, or tongue and grooyejoint, as in Fig. 9 at G,

'inthe use ot this device, the larger end of cone or sleeve 6 is adapted to be slipped over the truncated end ot' the core 5. thereby forming' a hollow extension of the same. The opposite end ot the cone (i may be supported conveniently by supplying a stud i' removably held in the neck oi the mold by a.

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cotter pin 7, Using this device I now proceed to cover core 5 and the cone G as well, with sheets of the plastic material indicated at- 8, which are formed thereabout and seamcd together in the ordinary or any desired manner, and the core with its hollow extension and plastic material therein may than be sari-minded oy the mold parts l, l.il and these bolted togther andto the core section. The mold is now ready to be placed in the vulcanizer whereupon vulcanization takes place in the ordinary way. After ren'ioval of the mold from the vulcanizer and unbolting the same, it will now be found that the mold sections l, l"L may be easily removed and the article, together with the hollow conical member or sleeve 6, may be removed as a unitary article from the core section El. The hollow conical member (3 thus becomes a reinforcement or lining, which remains permanently in the horn forming a part thereof, and as such por vides extra strength at the points where horns of this type are most liable to bend under their own weight in warm temperatures.

lt will, therefore, be seen that l have provided a horn having a reinforcement which materially strengthens the horn itself and is of further use in enabling the horn to be manufactured without the necessity of a core protruding entirely therethrough. EX- perinients have shown that such a horn is practicallyv as ellicient, as a conveyor of sound, as if it had been made entirely from cellular hard rubber, due to the fact probably that those portions of the horn in which the thickness of the material is comparatively small as compared to the diameter of the air column, are made entirely of cellular hard rubber, whereas those portions ot the horn in which the diameter oi the air column is small and therefore, the thiclzness of wall is larger compared therewith, have not as great an etl'ect upon the sound 1produced.

lt will be readily understood that my invention is not necessarily limited to the production of resonating horns, as similar hollow articles to be produced from cellular hard rubber might be made by the same process. It will also be apparent thatI other plastics might be employed in the manufacture of such articles with equal advantage.

Having thus described my invention, what l claim is l. rThe herein described method of making hollow articles of plastic material which consists in detachably connecting a core section and a liner section, applying a layer or layers of plastic material to the exterior 'face of the core and liner sections, en-

' said plastic layer in a mold, hardenthe article while conlined in the mold,

and thereafter removing the mold and core sections leaving the liner in place in the completed article.

2. The hereindescribed` method of making amplifiers of plastic material, which consists in detachably connecting a core section adapted to shape the interior of the larger end of the article to a hollow liner adapted to shape the interior of the balanre of the article, applying a layer olf plastic material to the exterior surface of the core and liner, enclosing the plastic layer in a mold, hardening the plastic n'iaterial, and thereafter removing the mold and core scctions leaving the liner in place.

il. A horn or amplifier of hardened plastic material having its .smaller end portion provided with al lining of non-plastic mate-A rial permanently united thereto.

el. A horn or amplifier of vulcanized ruhber having` a metallic liner covering the inner surface of the smaller portion thereof, and permanently secured thereto.

5. i'i horn or amplilier con'iposed of vull'inized cellular rubber having its neil; pro- 'L vided with a sheet metal liner.

i3. The method of making goose-necks. consisting in using a partial core associated with a sleeve to complete the core, placing the complete core in a mold, vulcanizing rubber in the mold around the core in the us' manner, removing the partial core, and leaving the sleeve in the goose-neck as an insert. r`he method oi making goose-necks, consi ting in, using a partial core, slipping a sleeve partlj,v over the core to complete the same, placing the complete core in a mold, vulcanizing rubber around the core in the usual manner, removing the partial core, and leaving the sleeve in the goose-neck.

The method of making goose-necks ol" plastic material, consisting in using a partial core, a sleeve to complete the said partial core, placing the complete core in a mold and placing said plastic material in said mold, or vice versa, removing said partial core when said plastic material has and leaving the sleeve in the goose-neclr'pernianently as an insert. l

l Si mold for bodies having irregular forms, comprising an exterior shell, aicore having a partial core portion removable from the molded body and a sleeve core portion not removable from the said molded body, the two said core portions having` a separable joint between them.

l0. i mold for bodies have irregular forms, comprising an exterior shell. a core having a partial core portion removalilc from the molded body and a sleeve core portion not removable from said molded boflv. the two said core portions having a telicscoping joint between them.

RICHARD T. GRIFFITHS. 

